1.7 Evolution

Question 1

Define ‘Evolution’

Answer 1

Evolution is the gradual change in the characteristics of an organism over many generations

Question 2

What is the difference between vertical and horizontal inheritance?

Answer 2

Vertical- passing of genetic material from parent to offspring
Horizontal- passing of genetic material across the same generation by transfer of plasmid between adjacent cells

Question 3

Give an example of an organism that can transfer genetic material through vertical or horizontal inheritance

Answer 3

Prokaryotes

Question 4

What are the three types of horizontal gene transfer?

Answer 4

<ul>
<li>Conjunction</li> 
<li>Transformation</li>
<li>Transduction</li>
</ul>

Question 5

What is an advantage of horizontal gene transfer?

Answer 5

Allows for rapid evolutionary change

Question 6

Describe the process of transformation horizontal gene transfer

Answer 6

Bacteria takes up naked bacteria from foreign cell

Question 7

Describe the process of conjunction horizontal gene transfer

Answer 7

• A conjunction bridge is formed between two adjacent cells allowing a plasmid to be copied and travel through the bridge to the adjacent cell

Question 8

Describe the process of transduction horizontal gene transfer

Answer 8

Phage inserts the viral DNA into the cell

Question 9

Define ‘Natural Selection’

Answer 9

Non random increase in the frequency of DNA sequences that increase survival chance of organism

Question 10

What is a deleterious sequence?

Answer 10

A deleterious sequence is a gene sequence that decreases the organism’s fitness

Question 11

How are deleterious sequences removed by natural selection?

Answer 11

Decrease the organism’s survival rate and so are selected against, meaning their frequency will decrease

Question 12

Define ‘Sexual Selection’

Answer 12

Non random increase in the frequency of DNA sequences that increase reproductive success of organism

Question 13

What are the three types of selection pressures?

Answer 13

Stabilising
Disruptive
Directional

Question 14

What selection pressure is baby weight an example of?

Answer 14

Stabilising

Question 15

What type of selection pressure favours the two extremes and is the driving force between sympatric selection?

Answer 15

Disruptive

Question 16

Describe Directional selection pressure

Answer 16

• favours one extreme
• shifts graph to left or right
• example: peppered moths

Question 17

What is the main difference between natural selection and genetic drift?

Answer 17

Natural Selection is non random, Genetic Drift is random

Question 18

Define ‘Genetic Drift’

Answer 18

RANDOM increase/decrease in the frequency of a DNA sequence in the gene pool of a population

Question 19

What are the mechanisms for Genetic drift

Answer 19

• Chance Events
• Neutral Mutations
• Founder Effect

Question 20

What is the founder effect?

Answer 20

The founder effect is where a small population becomes isolated and that small population has a gene pool that does not reflect the original population
Mechanism of Genetic Drift

Question 21

What is the Bottleneck effect?

Answer 21

This is where the majority of the population die out in a chance event(such as natural disaster) and the gene pool of the survivors does not reflect the original gene pool
Mechanism of Genetic Drift

Question 22

What is ‘Speciation’

Answer 22

The formation of a new species

Question 23

Why must populations be separated for speciation to occur?

Answer 23

So interbreeding is prevented

Question 24

Explain why genetic drift is more evident in smaller populations

Answer 24

Smaller populations so will have a bigger effect due to smaller gene pool

Question 25

What are the three main steps in speciation?

Answer 25

Isolation Mutation Natural Selection

Question 26

Describe what happens in the natural selection stage of speciation

Answer 26

Mutations may confer an advantage in habitat of population and so the the mutation will be selected for and will increase in frequency

Question 27

What are the two types of isolation barriers?

Answer 27

Geographical | Behavioural/Ecological

Question 28

What type of isolation barrier does sympatric selection need?

Answer 28

Behavioural/Ecological

Question 29

Describe Allopatric Selection

Answer 29

Formation of new species with a geographical barrier separating them

Question 30

How can scientists prove new species have been formed?

Answer 30

If two members of the populations breed and produce infertile offspring

Question 31

What is a hybrid zone?

Answer 31

A hybrid zone is an area of interbreeding between two closely related species

Question 32

What does a narrow hybrid zone represent?

Answer 32

Genetically distinct populations

Question 33

What would the width of the hybrid zone be if the populations were genetically

Answer 33

M